Piezoelectric device and circuitry

ABSTRACT

The present disclosure provides a device having a circuit. The circuit includes at least one boost converter receiving power from an energy source, a square wave driver in series with the boost converter, an inductor in series with the square wave driver for converting a square wave to a sinusoidal wave, and a piezoelectric transducer in series with the inductor, the piezoelectric transducer connectable to a load. The device further includes a phase-locked loop coupled to the circuit to determine a resonance frequency of the piezoelectric transducer when the piezoelectric transducer is connected to the load.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to, claims the benefit of, and incorporatesherein by reference U.S. Provisional Patent Application Ser. No.61/921,294 filed on Dec. 27, 2013 and entitled “Handheld UltrasonicInstrument,” and U.S. Provisional Patent Application Ser. No. 61/986,563filed on Apr. 30, 2014 and entitled “Handheld Ultrasonic Instrument”.

BACKGROUND OF THE INVENTION

The use of powered devices can enhance procedural efficiency andefficacy in the field of dentistry, including endodontic, periodontic,and hygiene procedures. For example, a powered device that providesultrasonic energy through a treatment tip can result in better cleaningand debridement of hard to reach areas or portions of teeth having acomplex geometry in these fields, as well as in oral surgery.

In various situations it can be useful to provide a wired or wirelessdevice for performing a dental or surgical procedure. Devices used inthe medical and dental fields such as endodontics, periodontics,hygiene, and other surgical procedures, oral or otherwise, aretraditionally performed using hand tools, or externally powered devices.Both are effective, but can have drawbacks. For example, the use of handtools can result in a lengthier procedure and cause pain, discomfort, orfatigue for the clinician, patient, or both. Powered devices alleviatethose problems and can be effective, but can introduce otherdifficulties. For example, powered devices with cords can be cumbersometo operate because of the fluid connections and cords that addappreciable weight to the device. Further, fluid connections and cordsassociated with the powered device can be difficult to manipulate duringthe procedure. During use, care must be taken to avoid tangling ofcords, occlusion of fluid pathways, or damage to either.

In the medical field, it can be useful to consider patient safety, timeof procedure, and efficacy in the surgical environment when developingnew tools and techniques. Like the dental field, powered devices canhave advantages over manually powered or unpowered hand tools, includingreducing procedure time and providing minimally invasive techniques.However, current powered devices can have drawbacks includinginsufficient operating life, heavier weight as compared with hand tools,and insufficient available power. Commercially available piezoelectricdevices for use in medical and dental procedures can include inefficientdrive circuitry that requires higher input power to achieve suitableresults. Excess energy is dissipated as heat or other losses, therebypotentially requiring large or higher rated circuit elements, heat sinksand a large device footprint. Previous piezoelectric scaler circuitdesigns used hard switching and power hungry approaches to forcemechanical resonance to occur at a defined electrical signal near themechanical resonance point. Typically, hard switching was accomplishedby connecting a transformer to the piezoceramic which was also connectedto “ground.” Such electrical circuits are lossy since the energy fromeach pulse charges the capacitive piezoceramic load and then the energyis discharged to ground. Examples of circuitry employing hard switchingfor driving ultrasonic devices can be found in U.S. Pat. Nos. 3,596,206,3,651,352, 4,445,063, and 4,168,447.

In yet another aspect, some prior cordless devices can be coupled to asource of fluid. In order to provide the fluid to the treatment site, apump, either remote from, or internal to the device, can be used.Internal electronic pumps draw power away from the power supply, whichin the case of a battery power supply can drain the battery morequickly.

The control center for existing devices can be located remotely, inwhich case the operator of the device can need to continually andsimultaneously support the device and adjust the control system, whichcan add time and require additional assistance to complete theprocedure. Also, alternating current (AC) powered devices can requirefeatures such as shielding from power line voltages and currents.

These and other problems can also arise during operation of anultrasonic device. Therefore, there is a need for a handheld ultrasonicdevice that overcomes the aforementioned drawbacks.

SUMMARY OF THE INVENTION

The present disclosure provides a device having a circuit. The circuitincludes at least one boost converter receiving power from an energysource, a square wave driver in series with the boost converter, aninductor in series with the square wave driver for converting a squarewave to a sinusoidal wave, and a piezoelectric transducer in series withthe inductor, the piezoelectric transducer connectable to a load. Thedevice further includes a phase-locked loop coupled to the circuit todetermine a resonance frequency of the piezoelectric transducer when thepiezoelectric transducer is connected to the load.

In one aspect, the energy source is a direct current rechargeablebattery, and is integral to the circuit. In another aspect, the circuitfurther includes a capacitor in series with the inductor for removingthe DC component of the piezoelectric transducer. In yet another aspect,the circuit further includes a capacitor in parallel with thepiezoelectric transducer to suppress at least a 3^(rd) harmonic mode ofvibration of the piezoelectric transducer. In a further aspect, thecircuit further includes a pair of back to back diodes in series withthe transducer to determine the phase of the current going through thetransducer so that it can be fed into the phase comparator of thephase-locked loop.

In one aspect, the circuit further includes a second boost converter inseries with the direct current battery. In another aspect, the output ofthe second boost converter is an input to the phase-locked loop. In afurther aspect, the load is a treatment tip for one of a dental and amedical procedure.

In another embodiment, the present disclosure provides a handheldultrasonic device including a device body having a distal end forcoupling to at least one treatment tip, and a circuit within the devicebody. The circuit includes, at least one boost converter, a square wavedriver in series with the boost converter, an inductor in series withthe square wave driver for converting a square wave to a sinusoidalwave, and a piezoelectric transducer in series with the inductor. Thedevice further includes a phase-locked loop in a feedback loop. Thephase-locked loop is coupled to the circuit to determine a resonancefrequency of the piezoelectric transducer when the piezoelectrictransducer is connected to the at least one treatment tip.

In one aspect, the circuit further includes an energy source. The atleast one boost converter is in series with the energy source. Inanother aspect, the circuit includes a second boost converter in serieswith the energy source. In yet another aspect, the output of the secondboost converter is an input to the phase-locked loop. In still anotheraspect, the handheld ultrasonic device further includes a fluid pump. Ina further aspect, the fluid pump is one of an elastomeric infusion pumpand a piezoelectric pump.

In one aspect, the circuit further includes at least one diode in serieswith the piezoelectric transducer. In yet another aspect, the handheldultrasonic device further includes a capacitor in series with theinductor for removing the DC component of the piezoelectric transducer.In a further aspect, the energy source is a rechargeable battery.

These and other aspects and advantages of the device and circuitrydisclosed herein will become better understood upon consideration of thedetailed description of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a handheld ultrasonicdevice with an attached fluid source according to the presentdisclosure;

FIG. 2 is an exploded view of the handheld ultrasonic device of FIG. 1;

FIG. 3 is a cross-sectional side view of the device of FIG. 1, takenalong line 3-3 of FIG. 1;

FIG. 4 is a side view of an embodiment of a piezoelectric transduceraccording to the present disclosure;

FIG. 5 a cross-sectional side view of the piezoelectric transducer ofFIG. 4, taken along the line 5-5 of FIG. 4;

FIG. 6 is an illustration of an embodiment of the internal circuitry ofthe device of FIG. 1 according to the present disclosure;

FIG. 7A is a first example schematic of the current flow through thecircuitry of FIG. 6;

FIG. 7B is a second example schematic of the current flow through thecircuitry of FIG. 6;

FIG. 8 is an illustration of another embodiment of the internalcircuitry of a device according to the present disclosure;

FIG. 9 is a schematic of the current flow through the dental devicecircuitry of FIG. 8;

FIG. 10 is a perspective view of a dental device according to thepresent disclosure attached to a remote fluid source;

FIG. 11 is a perspective view of a dental device according to thepresent disclosure with an attached fluid supply attached to one end ofthe device;

FIG. 12 is a perspective view of a dental device according to thepresent disclosure with an attached fluid supply;

FIG. 13 is an elevational side view of the fluid supply of FIG. 10;

FIG. 14A is a perspective view of a device according to the presentdisclosure illustrating the flow of fluid along an external fluid path;

FIG. 14B is a perspective view of a dental device according to thepresent disclosure illustrating the flow of fluid along an internalfluid path;

FIG. 15 is a side view of the fluid supply of FIG. 11 attached to asyringe;

FIG. 16 is a perspective view of the device of FIG. 12 showing the fluidsupply of FIG. 13 positioned apart from the device for attachmentthereto;

FIG. 17 is a perspective view of the device of FIG. 12 in use;

FIG. 18 is an enhanced view of FIG. 17 showing the device in use;

FIG. 19 is a perspective view of the device of FIG. 12 in a chargingstation;

FIG. 20 is a schematic of an example configuration of a circuitaccording to the present disclosure;

FIG. 21 is a perspective view of another embodiment of a deviceaccording to the present disclosure;

FIG. 22 is a cross-sectional side view of the device of FIG. 21 as takenalong line 7-7 of FIG. 21;

FIG. 23 is an exploded view of the device illustrated in FIG. 21;

FIG. 24 is a side view of the device illustrated in FIG. 21 showing afluid pump incorporated therein as indicated by dashed lines;

FIG. 25 is a plot of impedance as a function of phase angle for acommercially available piezoelectric transducer connected to a dentalhygiene treatment tip;

FIG. 26 is a schematic illustration of an electrical circuit equivalentto a piezoelectric transducer outside of mechanical resonance; and

FIG. 27 is a schematic illustration of an electrical circuit equivalentto a piezoelectric transducer at mechanical resonance.

DETAILED DESCRIPTION

Although the disclosure hereof is detailed and exact to enable thoseskilled in the art to practice the disclosure, the physical embodimentsherein disclosed merely exemplify the disclosure which can be embodiedin other specific structures. While the preferred embodiment has beendescribed, the details can be changed without departing from thedisclosure, which is defined by the claims.

In one aspect, the present disclosure relates to an efficient resonantpiezoelectric drive circuit for capacitive loads in piezoelectricultrasonic devices. The circuit can enhance the overall efficiency andefficacy of such devices, and the efficiency and efficacy of medical ordental procedures that employ such devices, such as an endodontic,periodontal, hygiene, or surgical procedures, including but not limitedto bone surgery and soft tissue surgery, or other operations which wouldbenefit from a resonant piezoelectric drive circuit capable ofdelivering mechanical output at ultrasonic frequencies. The capacitiveload can be connected in series to a drive voltage through an inductorand in parallel to a capacitor. Furthermore, the circuit can determinethe resonant frequency of a coupled piezoelectric transducer andtreatment tip. At resonance, reactive impedances can be reduced orminimized, thereby increasing or maximizing the energy transfer to thetreatment tip. However, the resonant frequency can vary depending on thetreatment tip. Accordingly, in some embodiments, the circuit can beuseful for a handheld ultrasonic device having a piezoelectrictransducer for use in a plurality of medical and dental operations.Further, embodiments of the present disclosure can provide forlightweight, compact, cordless, or versatile tools as compared withprior circuit and device designs. The described circuit can have a smallphysical footprint, require less energy, be powered with a compactrechargeable energy source, or a combination thereof. Circuits anddevices according to the present disclosure can be more energy efficientand may dissipate less energy as heat or other losses than othercircuits and devices. Moreover, a device according to the disclosure canwork with a various known or novel treatment tips. It is contemplatedthat circuits according to the present disclosure can be useful forinclusion in devices employed for other fields, as will be apparent toone of ordinary skill in the art.

FIG. 1 depicts an embodiment of a handheld ultrasonic device 10according to the present disclosure that is described in the context ofa dental device for use in dental procedures. However, the matterdisclosed herein can be utilized in other devices and procedures, asnoted. The device 10 generally includes a body 20 having a distal end 22and a proximal handle end 24. The proximal end 24 can connect to a powersource (not shown), that can be a rechargeable energy source such as asupercapacitor, a lithium ion, nickel cadmium or similar battery, acharging station (FIG. 17), or a combination of batteries and a chargingstation. The distal end 22 can accept various dental tips 110 (alsoreferred to as a treatment tip, surgical tip, dental hygiene tip, or thelike), typically via conventional attachment such as threads. Suitabletips include hardened stainless steel geometries that connect to thepiezoelectric transducer via threaded connections. Tips for thetransmission of ultrasonic energy according to the present disclosurecan be formed from materials such as stainless steel, aluminum, copper,brass, nickel, titanium, plastic composites, or a combination thereof.The portion of the tip used for treatment can include various physicalcharacteristics that can influence the cavitation effect of the devicesuch as flutes along the length of the file, tapering from the proximalto distal end of the file, a beveled edge, or the like. Cavitation canbe advantageous for various treatments, as cavitation can providesuperior cleaning and disinfection as compared with other techniques forcleaning and disinfection. In some embodiments, the present disclosurecontemplates the use of treatment tips that can create cavitation withinvarious treatment areas, including root canals, perio pockets or otherrestricted spaces where displacement of such a tip would be limited orconfined.

With reference to FIGS. 1-8, provided at least partially in the body 20are a power supply 80, a piezoelectric transducer 30, and circuitry 70that directs and controls power transmission from the power supply 80 tothe transducer 30. Nearly all piezoelectric transducers, also calledelectrostrictive transducers, have the same general construction, andinclude a piezoelectric stack assembly 50, a back mass 60, and a horn32. The entire assembly is resonant at a particular operating frequencywith the piezoelectric stack assembly 50 being only a small component ofthe overall assembly. Once assembled, the piezoelectric ultrasonictransducer 30 is resonant over its length. In some cases, this resonancecan be essential to proper operation. The transducer 30 isadvantageously shaped to minimize its length and width, whilemaintaining a desirable mechanical resonance frequency when loaded withthe dental tip 110 (typically about 25 kHz to about 50 kHz). The totallength L of the transducer 30 can be about 40 mm to about 60 mm.However, length L can vary for a particular use or a particular devicein which the transducer 30 is placed.

The piezoelectric stack assembly 50 includes at least one piezoelectricdisc 52 that can include piezoelectric ceramics or other materials suchas lead zirconate titanate, barium titanate, single crystal materialssuch as quartz, gallium phosphate, and tourmaline, or a combinationthereof. In the present example, the piezoelectric discs 52 are encasedor sandwiched between two metal back masses 60, and compressed by a boltor series of bolts through the center of the assembly or around theperimeter of the masses 60 to form a transducer 30 that amplifies thelateral displacement of the piezoelectric discs 52. In some embodiments,the piezoelectric materials are those suited for high-power acousticapplications. The result is the same—compression of the components ofthe transducer 30. The transducer 30 can have a cymbal transducer designin which the piezoelectric discs 52 are encompassed within two cymbalshaped metal plates that can be used to increase displacement.Alternatively, the transducer 30 can have a Moonie design in which thepiezoelectric discs 52 are provided between two metal back masses 60,thereby defining an internal crescent-shaped cavity. These surfaces areon the inner faces of the horn 32 and back mass 60 in direct contactwith the piezoelectric ceramic materials.

The piezoelectric stack assembly 50 has a stack first side 54 and astack second side 56 and includes piezoelectric discs 52. The transducertypically includes at least one piezoelectric disc 52, such as betweenabout 2 and about 8 discs, depending upon the application and thedesired operational characteristics. For example, two piezoelectricelements can be arranged to provide additive motion and can be arrangedso that their positive faces contact a center electrode insulated fromthe rest of the assembly. The remaining parts of the assembly includingthe stack first side and stack second side can be at negative or groundpotential and complete the circuit for the negative poles of thepiezoelectric elements. This arrangement can ensure that thepiezoelectric elements are connected electrically in parallel andmechanically in series.

The back mass 60 helps direct the mechanical vibration output by thepiezoelectric stack assembly 50 towards the horn 32. The back mass 60has a back mass first end 64 and a back mass second end 66. The backmass first end 64 abuts the piezoelectric stack second side 56.Additionally, the back mass 60 can include a solid body having a seriesof rings 62 of different radii. The different radii allow the back mass60 to provide the requisite performance characteristics of a similarlyperforming back mass of a uniform radius and a longer length. Therefore,the back mass 60 decreases the overall weight and length of the device10. Suitable materials for the back mass 60 include stainless steel,copper, brass, tungsten, titanium, aluminum, and combinations thereof.

The back mass 60 can extend through the piezoelectric stack assembly 50and horn 32. Additionally (or alternatively), a connector 48 can engagewith the horn second segment proximal end 44 and abut the back masssecond end 66 to secure the horn 32, the piezoelectric stack 50, and theback mass 60 together.

The horn 32 amplifies mechanical vibrations output by the piezoelectricstack assembly 50. The horn 32 can include titanium, stainless steel,aluminum or another suitable metallic alloy and can have a horn firstsegment 34 and a horn second segment 40 adjoining the horn first segment34. The horn first segment 34 has a horn first segment proximal end 36and a horn first segment distal end 38. The horn first segment proximalend 36 substantially abuts the piezoelectric stack first side 54. Thehorn first segment 34 is substantially frustoconical and is tapered fromthe horn first segment proximal end 36 towards the horn first segmentdistal end 38. The tapered horn first segment 34 promotes amplificationof the ultrasonic energy towards the horn first segment distal end 38.The horn first segment distal end 38 can include threads 12, or a quickconnect (not shown), that securably connects to and is received by thedental tip 110.

Additional or alternative horn shapes are contemplated wherein asatisfactory amplification of the ultrasonic energy can be achieved. Forexample, horn designs that would obviate the need for the treatment tipto contain a counterangle are described herein. In one example, a hornshape includes a prebent shaft having a bend between about 50 degreesand about 90 degrees with male threads. Another design includes anangular cut and female threads on the distal end of the horn to allowfor tip attachment. Moreover, the horn second segment 40 can include ahorn second segment distal end 42, adjoining the horn first segmentproximal end 36, and a horn second segment proximal end 44. The hornsecond segment 40 can be substantially cylindrical.

When a piezoelectric material is properly cut and mounted to create atransducer, it can be made to distort in an electric field(electrostriction or inverse piezoelectricity) by applying a voltage toan electrode near or on the crystal. Upon the application of voltage,the piezoelectric discs 52 experience morphological change, therebyconverting electric pulses to mechanical vibration output through thedental tip 110.

Apart from mechanical resonance, the piezo transducer 30 can be mostlycapacitive in nature because piezoelectric elements in the transducerare arranged between electrodes and the piezoelectric elements serve asthe dielectric, thereby forming a capacitor. At resonance, thepiezoelectric transducer 30 can be modeled as an electrical equivalentcircuit that behaves like a circuit composed of an inductor, capacitor,and resistor with a precise resonant frequency (FIG. 27). When the fieldis removed, the crystal will generate an electric field as it returns toits previous shape, and this can generate a voltage. The electricalcircuit equivalent of the piezo transducer describes the change inmechanical properties, such as elastic deformation, effective mass(inertia), and mechanical losses resulting from internal friction.However, this description of the piezoelectric transducer can only beused for frequencies in the vicinity of the mechanical intrinsicresonance. By changing the dimensions and contours of the transducermasses, or by changing how the transducer is loaded, the operatingfrequency along with electrical and acoustic characteristics can becustomized for specific applications.

Further amplification and mechanical efficiency of the transducer can beaccomplished using known techniques, such as changing the internal facesof the masses that contact the piezoelectric elements to help propagateultrasonic waves through the masses. Shallow cavities on the innersurfaces of the masses can create a mechanical transformer, whereby aportion of the radial motion of the ceramic driving elements istransferred and amplified by the metal plates in axial direction.

Referring again to at least FIGS. 1-3, the body 20 can support aninternal (not shown) or external fluid source 92, shown as coupled tothe body 20 via a port or connector 94 that can include threads, a luerattachment, a quick connect feature or any other suitable attachmentfeature. The transducer 30 can include a through channel 46 (FIG. 14B)extending through the horn first segment 34 and the horn second segment40. FIG. 3 further illustrates the connection of the internal fluid line90 from the connector 94 to or through the piezoelectric transducer 30.Fluid can flow from the fluid supply 92 (see FIG. 2) through the insideof the device 10 via the internal fluid line 90 and the horn throughchannel 46 and out though the dental tip 110. Other fluid configurationsare described infra.

The aforementioned circuitry 70 confers particular advantages on devicesin accord with the disclosure. The circuitry 70 generally includes aboost converter 68, a phase comparator 72, a low pass filter 76, avoltage controlled oscillator (“VCO”) 74, and a feedback network 78. Theelectronic circuitry 70 can drive the transducer 30 at its mechanicalresonance. FIGS. 7A and 7B show a flow diagram of a potential electricalpath through the device 10. FIG. 7B incorporates schematic symbols forthe phase comparator 72, a low pass filter 76 and the VCO 74. Thecircuitry 70 can also include the power supply 80, shown here as a DCpower source. The power supply can include at least one battery. In oneembodiment, the battery is a single cell lithium ion battery with anenergy capacity of about 2 to about 10 Watt-hours and is capable ofsupplying an output current of between about 0.5 A and about 3 A duringoperation. Additionally, it is contemplated that the at least onebattery can be rechargeable either by direct electrical contactcharging, induction charging, or a combination thereof (see FIG. 19).Moreover, the circuitry 70 or 170 can include one or more protectivecomponents 75 such as one or more inductors, one or more diodes, or acombination thereof.

In some embodiments, the circuitry 70 includes an LC tank circuit or LCelectrical resonator. In general, an LC tank circuit can have afrequency selective filter including an inductor (L) and capacitor (C)connected together. The LC tank circuit shown and described herein moreefficiently drives the piezoelectric transducer. The circuit can be selfadjusting to drive the transducer at its mechanical resonance. Chargeflows back and forth between the capacitor's plates through theinductor, so the tuned circuit can store electrical energy oscillatingat its resonant frequency. There are small losses in the “tank” (i.e.,LC) circuit, but the amplifier feed by the signal from the VCOcompensates for those losses and supplies the power for the outputsignal to compensate for the electrical and mechanical losses of thesystem. This combination and arrangement of circuit elements results ina low power consumption electronic circuit. By driving the transducer ator near resonance and by using the series inductor the circuit drivinglosses can be minimized. Further the system can have a high “Q”. Forexample, one such circuit design is capable of generating a drive with a“Q” of about 5 to about 20. In this case Q=Gain (G)=about 5 to about 20.Therefore, about ⅕ to about 1/20 of the power is required for apiezoelectric scaler according to the present disclosure to produce thesame work output of a design including hard switching.

It can be advantageous to select the circuit elements of the inductorand capacitor so that their resonance frequency is higher than that ofthe mechanical resonance of the piezoelectric transducer, but less thanthe 3rd harmonic mechanical resonance of the piezoelectric transducer.If the 3rd harmonic mechanical resonance (or higher order harmonics) isnot appropriately filtered by the combination of Lser and Cpar, 3rdharmonic oscillations can become dominant in the drive waveform andyield nonuseful and nonproductive mechanical output on the piezotransducer. For dental and medical piezoelectric devices, the resonancefrequency of the added LC tank circuit can be in the range of about 60kHz to about 120 kHz. Furthermore, the capacitance can be selected sothat it is larger than the parallel capacitance of the piezoelectrictransducer not at resonance. In one example, a 10 mm outerdiameter.times.5 mm inner diameter.times.2 mm height piezoelectricceramic disc element has a capacitance value around 300 pF. Apiezoelectric transducer incorporating a stack of 4 piezoelectriccrystals would have an approximate value of about 1.2 nF, so a suitablecapacitance value would be about 4.7 nF. These parameters can restrictthe allowable inductance value to between about 0.37 mH and about 1.5mH, providing a resonance frequency in the above-specified ranges.

FIG. 8 is an example illustration of an embodiment 170 of the circuitryof the device 10. Here, the circuitry 170 includes an inverter 172, anda frequency divider 174. Additional circuit elements can provide theability to regulate both incoming and outgoing voltage.

FIG. 9 illustrates a general schematic illustrating one potential flowof current through the device 10 according to the embodimentincorporating the circuitry 170 illustrated in FIG. 8. Here, currentflows from the power supply 80 to the inverter 172. Preferably, theapplied voltage is delivered in a sine wave or impulse waveform in theMegahertz range. The inverter 172 thereby inverts the incoming directcurrent from the battery 80 to achieve this.

Supplying power at a frequency in the Megahertz range can be moreefficient and enable the use of smaller electrical components ascompared with the use of other frequencies. However, it can be useful tooperate a device or circuit according to the present disclosure at analternative or additional operational frequency. In one aspect, thecurrent can be passed through the frequency divider 174 to alter theinput signal and output a signal frequency that is a fraction of theinput signal frequency. In one aspect, the output signal can be in thekilohertz range. In another aspect, the output signal can be selected toprovide an operational frequency that is matched to the mechanicalresonance of the transducer when loaded. Furthermore, it is contemplatedthat current can first flow from an alternating current source 118,through a transformer, rectifier, filter, and regulator (collectively120) to recharge the at least one battery 80.

Additionally, it should be noted that alternative current paths capableof achieving the operation characteristics described herein are alsocontemplated. For instance, current can also flow to or from a switch, acontrol device, or a combination thereof positioned somewhere along thecurrent path, the location of which can be based on optimization of thecircuitry 70 and transducer 30 components.

FIG. 20 is a demonstrative illustration of an alternative configuration200 of the circuitry 70 of the device 10. The circuitry of the device 10in this alternative configuration 200 includes a battery 202 connectedbetween a ground 242 a and a first boost converter 204 and a secondboost converter 206. The first boost converter 204 is connected to afirst ground 242 b and the second boost converter 206 is connected to asecond ground 242. The output of the first boost converter 204 isbetween about 20 V to about 200 V and leads to a square wave driver 208.The output of the second boost converter 206 is about 5 V and providespower to a phase-locked loop (PLL) 238. The square wave driver 208,which generates a high voltage square wave output 209, is in series witha capacitor 210 and an inductor 212. The inductor 212 converts thesquare wave output 209 into a sine wave output 213.

The combination of the capacitor 210 and the inductor 212 is connectedin series with a piezoelectric transducer 218. The capacitor 210 canremove the DC component from the piezoelectric transducer 218. Thepiezoelectric transducer 218 is connected in series with a first diode220 and a second diode 222. The first diode 220 and a second diode 222can be Schottky diodes. The first diode 220 and the second diode 222 areconnected in parallel with each other and are connected to respectivegrounds 242 f and 242 g. The junction of the piezoelectric transducer218, the first diode 220, and the second diode 222 is one input to avoltage comparator 224, with the other input to the voltage comparator224 being a ground 242 h.

The output of the voltage comparator 224, which can indicate thedirection and phase of the current in the circuit 200, is an input tothe phase comparator (in PLL 238). The output of the phase comparatorgoes to the low pass filter that includes resistor 234 and capacitor 236which feeds into a voltage-controlled oscillator (VCO) 240. The PLL 238includes the combination of the phase comparator, low pass filter, andVCO 240. The output of the voltage-controlled oscillator 240 is anotherinput to phase comparator 238 and is also an input to the square wavedriver 208. Block 244 includes a frequency limiting circuit. If adisturbance causes the system's frequency to exceed the resonantfrequency of the crystal, the phase can get switched, and the PLL 238can run into an upper rail. This can be detected by monitoring thevoltage on the low pass filter. If the voltage approaches the upperrail, the voltage can be momentarily pulled back to ground (the lowestoperating frequency) and released so the PLL 238 can once again acquirefrequency lock on the crystal. Other possible limiters such as acomparator with appropriate feedback networks can also be used.

The phase lock loop synchronizes the drive voltage to the phase of thecurrent through the ceramic. The PLL 238 detects where the impedance isthe lowest or where the phase crosses zero (i.e. where the reactiveelements—capacitor and inductor—become electrically a short circuit andthe phase between the input and output waveforms is a zero phase shift).

The piezoelectric transducer 218 operates at a higher unloaded resonancefrequency, but when loaded by a surgical or treatment tip, operateswithin the range of about 25 kHz to about 50 kHz. The surgical ortreatment tip can be any tip designed for the transmission of ultrasonicenergy when coupled to a piezoelectric device. For example, a suitabletreatment tip can include any tip for use with current dental scalerdevices. In one aspect, a treatment tip can be a flexible, bendable, orrigid ultrasonic tip to allow for a user to define the contra-angle andstill provide adequate energy transfer. Circuitry according to thepresent disclosure can omit a smoothing circuit, as the combination ofthe capacitor 210 and the inductor 212 can create the sinusoidal driveoutput signal 213. It can be useful to provide a sinusoidal drive toreduce the rate of wear on a treatment tip, improve patient comfort, ora combination thereof.

FIGS. 10-12 illustrate additional fluid delivery embodiments. FIG. 10shows a remote fluid source 82 and an external fluid line 84. Theexternal fluid line 84 can be removably secured to the device 10 by wayof clips 86 or other suitable attachment methods. Turning to FIG. 14A,fluid 112 flows from the remote fluid source 82, through the externalfluid line 84, to the procedure site either through the interior of thedental tip 110 as shown here or along the exterior of the dental tip110. Additional or alternative methods of fluid delivery are alsocontemplated. For example, the fluid can initially travel through anexternal bore of a treatment tip before flowing towards to the exteriorof the treatment tip in order to flow along an exterior surface thereof.

FIG. 11 illustrates a collinear fluid supply 88, which can be anelastomeric pump, removably attached to the end of the device oppositethe dental tip 110. A fluid inlet (not shown) can be located oppositethe location of attachment to the device 10 to allow filling of thecollinear fluid supply 88 while attached to the device 10. Fluid 112 canflow external to the device 10 (see FIG. 14A) or can flow through thedevice 10 by way of an internal fluid line 90 and the through channel 46(see FIG. 14B) and out through the dental tip 110. Additionally, thepower switch 130 is shown positioned on the body 20 of the device 10 inthis embodiment.

FIG. 12 shows a radially mounted fluid source 92 that can include afillable non-powered fluid source 100. As a non-limiting example, thenon-powered fluid source shown here is an elastomeric pump. However, anydevice capable of using potential energy to expel liquid from itsinterior by the nature of the container material's elasticity iscontemplated. The elastomeric pump 100 includes an input 102, anelastomeric bladder 104, and an output 106 (see FIG. 13). The input 102can be configured to receive a syringe 122 (see FIG. 15) and can includea one-way valve. The output 106 can also include a one-way valve and canbe removably attached and operatively connected to the internal fluidline 90 through a connector 94 located on the periphery of the device10.

The non-powered fluid source 100 promotes a constant flow rate of thefluid 112 by expending potential energy stored in a filled elastomericbladder 104. The fluid 112 can be delivered to and through the device 10without the need of electricity and separate from the power source andthe piezoelectric stack thereby reducing the overall electricity demandof the device 10.

FIG. 14B illustrates the flow path of the fluid from the radiallymounted fluid source 92 through the device 10. The fluid can include anynumber of dental solutions including water, saline, bleach, CHX, EDTA,Listerine, Peridex, and other solutions commonly used in prophylaxis andother dental procedures. First, the fluid 112 exits the output 106 ofthe elastomeric infusion pump 100 and travels through the internal fluidline 90. The internal fluid line 90 can operatively connect with orextend through the transducer through channel 46. The fluid 112 thenflows through the connected dental tip 110 and out to the proceduresite.

FIGS. 15-18 show the operation of the device 10. In FIG. 15 the fluidsource 100 is filled by a syringe 122. The interface between the syringe122 and the fluid source 100 can be accomplished by way of a luer lockfitting or any way known in the art.

FIG. 16 illustrates the attachment of the elastomeric infusion pump 100to the device 10. A luer lock fitting or comparable fitting can be usedin this interface as well.

As shown in FIG. 17, the device 10 is shown in an operator's hand 114with the dental tip 110 located at or near the procedure site. FIG. 18further illustrates the mechanical operation of the transducer 30 andthe dental tip 110. The preferred voltage applied to piezoelectric stack50 is about 100 V to about 800 V peak-to-peak. The vibrations created bythe linear movement of the piezoelectric stack 50 are carried throughthe horn 32 and out to the dental tip 110 resulting in an oscillatorymovement. The fluid 112 enters the procedure site, for example, throughthe dental tip 110.

FIG. 19 exemplifies a charging station 116 that can be plugged into anystandard A/C outlet (e.g., 120V or 240V) to recharge the power supply80. The power supply can alternatively be recharged by direct electricalcontact charging or by induction charging.

Another configuration of the device 10 is shown in FIGS. 21-24. FIG. 21illustrates a perspective view of a device 300. The device 300 has abody 302 having a distal end 304 and a proximal end 306, an activationbutton 308, and a surgical or treatment tip 310.

As shown in FIG. 22, the device body 302 supports the circuitry 312 andthe rechargeable energy source 313 at the proximal end 306 of the device300. The circuitry 312 can be similar or identical to the circuitry 200shown in FIG. 20. The rechargeable energy source can be a DC battery, asupercapacitor, a rechargeable battery, a lithium ion battery, the like,or combinations thereof. In one aspect, the rechargeable energy sourcecan be combined with or omitted in place of any other energy sourceknown in the art. In one embodiment, the rechargeable energy source canbe omitted from the device, for example, in the case of a wired devicethat is electrically connected to an external energy source such as anexternal battery or a building outlet. In some embodiments, the body 302can support a piezoelectric transducer 314 at the distal end 304 of thedevice 300. The piezoelectric transducer 314 can be similar or identicalto the piezoelectric transducer 30 shown in FIG. 5.

FIG. 23 shows body 302 that includes a plurality of sections, forexample the five sections 302A, 302B, 302C, 302D, and 302E that can snaptogether using clips 316 or joined with screws. The sections areconfigured to house the circuitry 312, the battery 313, and thepiezoelectric transducer 314 so that the circuitry 312 and the battery313 are tightly in place and the piezoelectric transducer 314 hasfreedom to move as needed.

Turning to FIG. 24, the fluid pump 318 can be, e.g., an elastomericinfusion pump or a piezoelectric pump of the type available fromDolomite Microfluidics, CurieJet, Schwarzer Precision, Takasago FluidicSystems, and Bartels Mikrotechnik. However, other piezoelectric pumpsthat meet the power, size and flow rate requirements of the device arecontemplated. In one embodiment, a piezoelectric pump can provide fluiddelivery and irrigant flow rates of about 0.01 mL to about 20 mL perminute and consume power less than about 500 mW during operation. Inanother embodiment, a piezoelectric pump can provide fluid delivery andirrigant flow rates of about 2 mL to about 10 mL per minute. The fluidpump 318 can be configured to pump a fluid, such as water, through thedevice 300 by way of fluid line 320. The fluid can flow through fluidline 320 and the piezoelectric transducer 314 and the tip 310. In otherconfigurations, the fluid pump 318 is not incorporated into the device300 and can either be attachable to the device 300 or partially orcompletely external and connected to the device via a separate fluidline. Regardless of the fluid path, the device 300 can incorporatematerials that are compatible with the aforementioned irrigants and canrequire further processing of the metallic parts to ensure reliabilityof the device 300.

The device 300 can be controlled by a wired or wireless foot pedal, acentral control unit that operates wirelessly to the handheld device, orby another similar means so as to control the ‘on’ and ‘off’ operationsof the device 300, power setting (in other words, applied voltage topiezoelectric ceramic), and fluid delivery flow rates commonly observedin tethered bench top units.

EXAMPLES

With reference to FIG. 25, an example device according to the presentdisclosure having a circuit as shown in FIG. 20 was loaded with atreatment tip. The treatment tip was an ultrasonic dental hygienescaling tip designed for removal of dental plaque and calculus build up,and was securably coupled to the ultrasonic dental transducer headpiecewith a torque wrench. The leads to the ultrasonic handpiece were thenconnected to an impedance analyzer to obtain electrically equivalentcircuit parameters and features related to the mechanical resonance ofthe coupled handpiece and treatment tip system. Impedance and phasespectra were collected by a Bandera PV70A impedance analyzer designedfor collecting data from high power ultrasonic transducers. The resonantfrequency (F_(s)) was determined to be 27,536 Hz by identifying wherethe impedance is a local minimum and the phase is zero. Furtherparameters related to the present example are shown in Table 1 below.Based on the measured values for C_(T) and F_(S), suitable parametersfor the parallel capacitor and series inductor are as follows: Cpar=4.7nF and Lser would be between about 1.0 mH and about 5.25 mH to ensurethat the combined Lser+Cpar resonance frequency is larger than themechanical resonance of the transducer, but less than the 3^(rd)harmonic mechanical resonance (i.e. 27,536 Hz and 82,608 Hz,respectively).

TABLE 1 Parameter Units Value F_(s) Hz 27536.0 F₁ Hz 27518.2 F₂ Hz27553.6 Q_(m) — 777.8 G_(max) Ms 2.67 R₁ Ohm 374.7 F_(p) Hz 27750K_(eff) — 0.124 C_(T) nF 1.350 C₀ nF 1.330 C₁ nF 0.020 L₁ mH 1684.6Z_(max) kOhm 48.7 F₀ — 27643

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, an and the are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The description of the present disclosure has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. Explicitly referenced embodiments herein were chosen anddescribed in order to best explain the principles of the disclosure andtheir practical application, and to enable others of ordinary skill inthe art to understand the disclosure and recognize many alternatives,modifications, and variations on the described example(s). Accordingly,various embodiments and implementations other than those explicitlydescribed are within the scope of the following claims.

What is claimed is:
 1. A cordless handheld device, comprising: a drivecircuit, comprising: at least one boost converter receiving power froman energy source; a square wave driver in series with the boostconverter; an inductor in series with the square wave driver forconverting a square wave to a sinusoidal wave; and a piezoelectrictransducer in series with the inductor, the piezoelectric transducerconnectable to a load and having a capacitance, a mechanical resonancefrequency, and a 3rd harmonic mode of vibration; a phase-locked loopcoupled to the drive circuit and configured to synchronize drive voltageto the resonance frequency of the piezoelectric transducer when thepiezoelectric transducer is connected to the load; and a frequencylimiting circuit coupled to the phase-locked loop.
 2. The device ofclaim 1, wherein the energy source is a direct current rechargeablebattery, and wherein the energy source is integral to the circuit. 3.The device of claim 2, wherein the circuit further comprises a secondboost converter powered from the direct current battery.
 4. The deviceof claim 3, wherein the output of the second boost converter providespower to the phase-locked loop.
 5. The device of claim 1, wherein thecircuit further comprises a capacitor in series with the inductor forremoving the DC component of the piezoelectric transducer.
 6. The deviceof claim 1, wherein the circuit further comprises a capacitor inparallel with the piezoelectric transducer to suppress at least a 3^(rd)harmonic mode of vibration of the piezoelectric transducer.
 7. Thedevice of claim 6, wherein the capacitor has a capacitance larger thanthe piezoelectric transducer capacitance and a resonance frequency withthe inductor higher than the mechanical resonance frequency, but lowerthan the 3rd harmonic mode of vibration, of the piezoelectrictransducer.
 8. The device of claim 1, wherein the circuit furthercomprises a pair of back to back diodes in series with the transducer todetermine the phase of the current going through the transducer so thatit can be fed into the phase comparator of the phase-locked loop.
 9. Thedevice of claim 1, wherein the load is a treatment tip for one of adental and a medical procedure.
 10. The device of claim 1, wherein thefrequency limiting circuit monitors voltage on a low pass filter toprevent the phase-locked loop from exceeding the resonant frequency ofthe piezoelectric transducer.
 11. A cordless handheld ultrasonic devicecomprising: a device body having a distal end for coupling to at leastone treatment tip; and a drive circuit within the device body, thecircuit comprising: at least one boost converter; a square wave driverin series with the boost converter; an inductor in series with thesquare wave driver for converting a square wave to a sinusoidal wave;and a piezoelectric transducer in series with the inductor and having acapacitance, a mechanical resonance frequency, and a 3rd harmonic modeof vibration; a phase-locked loop in a feedback loop, the phase-lockedloop coupled to the drive circuit and configured to synchronize drivevoltage to the resonance frequency of the piezoelectric transducer whenthe piezoelectric transducer is connected to the at least one treatmenttip; and a frequency limiting circuit coupled to the phase-locked loop.12. The handheld ultrasonic device of claim 11, wherein the circuitfurther comprises an energy source, the at least one boost converter inseries with the energy source.
 13. The handheld ultrasonic device ofclaim 12, wherein the energy source is a rechargeable battery.
 14. Thehandheld ultrasonic device of claim 11, wherein the circuitry furthercomprises a second boost converter in series with the energy source. 15.The handheld ultrasonic device of claim 14, wherein the output of thesecond boost converter is an input to the phase-locked loop.
 16. Thehandheld ultrasonic device of claim 11, further comprising a fluid pump.17. The handheld ultrasonic device of claim 16, wherein the fluid pumpis one of an elastomeric infusion pump and a piezoelectric pump.
 18. Thehandheld ultrasonic device of claim 11, wherein the circuitry furthercomprises at least one diode in series with the piezoelectrictransducer.
 19. The handheld ultrasonic device of claim 11, furthercomprising a capacitor in series with the inductor for removing the DCcomponent of the piezoelectric transducer.
 20. The device of claim 11,further comprising a capacitor in parallel with the piezoelectrictransducer, the capacitor having a capacitance larger than thepiezoelectric transducer capacitance and a resonance frequency with theinductor higher than the mechanical resonance frequency, but lower thanthe 3rd harmonic mode of vibration, of the piezoelectric transducer. 21.The device of claim 11, wherein the frequency limiting circuit monitorsvoltage on a low pass filter to prevent the phase-locked loop fromexceeding the resonant frequency of the piezoelectric transducer.